Study of Photophysical Properties on Newly Synthesized Coumarin Derivatives.

Herein, we have studied the photophysical properties for three newly synthesized coumarin derivatives; 4-((2,6-dibromo-4-methylphenoxy)methyl)-2H-benzo[h]chromen-2-one (DMB), 4-((3,4-dihydro-6,7-dimethoxyisoquinolin-1-yl)methyl)-6-methyl-2H-chromen-2-one (DIM) and 4-((p-tolyloxy)methyl)-6-methoxy-2H-chromen-2-one (TMC). The absorption and emission spectra for above said molecules were recorded in different solvents at room temperature in order to calculate their ground and excited state dipole moments. The ground (µ g ) and excited state dipole (µ e ) moments of these coumarin derivatives were calculated using Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations by the solvatochromic shift method, which involves a variation of Stokes shift with the solvent dielectric constant and refractive index. Ground state dipole moments (µ g ) were also calculated from the Guggenheim method using the dielectric constant and refractive index of the solute molecule. The value of ground state dipole moment obtained from these two methods is well correlated. Further, it is notified that the excited state dipole moment is larger than the ground state dipole moment for all three solute molecules. It inferred that the excited state for above said molecules is more polar than the ground state. The present investigations may shine in the design of nonlinear optical materials. Graphical Abstract The photophysical properties for novel coumarin derivatives were studied in different solvents.Ground and excited state dipole moments were estimated by the solvatochromic shift method. The excited state dipole moment is greater than the ground state dipole moment in systems studied. The excited state is more polar than the ground state. The present investigation may be shine in the design of non linear optical materials.

Photophysical Properties of a Novel and Biologically Active 3(2H)-Pyridazinone Derivative Using Solvatochromic Approach.

Herein, we report photophysical properties of a novel and biologically active 3(2H)-pyridazinone derivative 5-(4-chloro-2-hydoxy-phenyl)-2-phenyl-2H-pyridazin-3-one [CHP] molecule using solvatochromic approaches. Absorption and fluorescence spectra of CHP molecule have been measured at room temperature in various solvents of different polarities. From this, it is observed that the positions, intensities and shapes of the absorption and emission bands are usually modified. Experimentally, the ground and excited state dipole moments are estimated using solvatochromic shift method which involves Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations. Theoretically, the ground state dipole moment was estimated using the Gaussian-09 program. The value of ground state dipole moment estimated using experimental and theoretical methods are well correlated. This inference that the molecular geometry is taken for CHP molecule under theoretical and experimental methods are similar. Further, we observed that the excited state dipole moment (µ e ) is greater than the ground state dipole moment (µ g ) which indicates that the excited state is more polar than the ground state. Furthermore, we have estimated an angle between the ground and excited state dipole moments. In addition, we have estimated the fluorescence quantum yield of CHP molecule using Rhodamine B as a standard reference in different solvents.

Analysis of Fluorescence Quenching for Newly Synthesized Biologically Active 3(2H)-pyridazinone Derivative by Aniline.

Herein, we have studied the analysis of fluorescence quenching for newly synthesized biologically active 3(2H)-pyridazinone derivative 5-(5-bromo-2-hydroxy-phenyl)-2-phenyl-2H-pyridazin-3-one [BHP] by various concentrations of aniline using UV-Visible spectroscopy, fluorescence spectroscopy and time-correlated single photon counting technique in five different solvents namely, methanol, ethanol, propan-2-ol, dimethylsulfoxide and ethyl acetate at room temperature. The fluorescence intensity of BHP molecule decrease with increasing in the aniline concentration and it is studied using the Stern-Volmer relation. The obtained Stern-Volmer plots were found to be linear in all the five solvents. The various parameters responsible for the fluorescence quenching such as quenching rate parameters (k q ), diffusion rate parameter (k d ) and the probability of quenching per encounter (p) were experimentally calculated in all five solvents. An activation energy of quenching (E a ) was calculated using the values of activation energy of diffusion (E d ) and p. It was found that the values of E a are greater than E d in all five solvents studied. Further, it is inferred that the fluorescence quenching reactions in BHP molecule are more significantly affected by activation energy processes.

Effect of TiO2 nanoparticles on some photophysical characteristics of ketocyanine dyes.

The effect of titanium dioxide (TiO2 ) nanoparticles (NPs) on photophysical characteristics of 2,5-di[(E)-1-(4-dimethylaminophenyl) methylidine]-1-cyclopentanone (2,5-DMAPMC) and 2,5-di[(E)-1-(4-diethylaminophenyl)methylidine]-1-cyclopentanone (2,5-DEAPMC) ketocyanine dyes has been studied using absorption, steady-state and time-resolved fluorescence spectroscopy. The magnitudes of association constants determined based on modified absorption spectrum of dyes due to the presence of TiO2 NPs indicate the interaction of TiO2 NPs with dye molecules. The quenching of fluorescence intensity of dyes by TiO2 NPs is observed and it follows linear Stern-Volmer (S-V) equation. The magnitude of quenching rate parameter suggests the involvement of static quenching mechanism. The involvement of electron transfer process in reducing fluorescence intensity of dyes has been discussed. Also, varying influence of TiO2 NPs on two dyes is explained based on the presence of different alkyl substituent in two dyes.

Solvent Effects on the Electronic Absorption and Fluorescence Spectra of HNP: Estimation of Ground and Excited State Dipole Moments.

We report the effect of solvents on absorption and fluorescence spectra of biologically active 3(2H)-pyridazinone namely 5-(2-hydroxy-naphthalen-1-yl)-2-phenyl-2H-pyridazin-3-one (HNP) in different solvents at room temperature. The ground and the excited state dipole moments of HNP molecule was estimated from Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations using the solvatochromic shift method. The ground state dipole moment (µ g ) was also estimated by Guggenheim and Higasi method using the dielectric constant and refractive index of solute at different concentrations, the µ g value obtained from these two methods are comparable to the µ g value obtained by the solvatochromic shift method. The excited state dipole moment (µ e ) is greater than the ground state dipole moment (µ g ), which indicates that the excited state is more polar than the ground state. Further, we have evaluated the change in dipole moment (Δµ) from the solvatochromic shift method and on the basis of molecular-microscopic solvent polarity parameter[Formula: see text], later on the values were compared.

Crystal structure of 7,8-benzocoumarin-4-acetic acid.

The fused-ring system in the title compound [systematic name: 2-(2-oxo-2H-benzo[h]chromen-4-yl)acetic acid], C15H10O4, is almost planar (r.m.s. deviation = 0.031 Å) and the Car-C-C=O (ar = aromatic) torsion angle for the side chain is -134.4 (3)°. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, generating [100] C(8) chains, where the acceptor atom is the exocyclic O atom of the fused-ring system. The packing is consolidated by a very weak C-H⋯O hydrogen bond to the same acceptor atom. Together, these inter-actions lead to undulating (001) layers in the crystal.

Investigation of role of silver nanoparticles on spectroscopic properties of biologically active coumarin dyes 4PTMBC and 1IPMBC.

The role of silver nanoparticles on spectroscopic properties of biologically active coumarin dyes 4-p-tolyloxymethyl-benzo[h]coumarin (4PTMBC) and 1-(4-iodophenoxymethyl)-benzo[f]coumarin (1IPMBC) has been investigated using absorption and fluorescence spectroscopy. Silver nanoparticles are synthesized by chemical reduction method and the estimated size by Mie theory is 12 nm. The absorption spectral changes of dyes in the presence of silver nanoparticles suggest their possible interaction with silver nanoparticles. The apparent association constants of the interaction are estimated using Benesi-Hildebrand model. Fluorescence quenching has been observed in both the dyes with the addition of silver nanoparticles. The Stern-Volmer plots of fluorescence quenching are found to be nonlinear showing positive deviation. The magnitudes of quenching rate parameter and fluorescence lifetime measurements indicate the presence of both collisional and static quenching mechanisms. The binding constants and the number of binding sites for the static type of quenching have been estimated from the fluorescence data. The role of diffusion, energy transfer and electron transfer processes in fluorescence quenching mechanism has been discussed.

Photophysical characteristics of biologically active 4-aryloxymethyl coumarins 4PTMBC and 1IPMBC.

The absorption and fluorescence characteristics of biologically active coumarin derivatives 4-p-tolyloxymethyl-benzo[h]coumarin (4PTMBC) and 1-(4-iodo phenoxymethyl)-benzo[f]coumarin (1IPMBC) are studied at room temperature in a series of organic solvents and 1,4-dioxane - acetonitrile solvent mixture. The effect of pure solvents on the spectral properties are analyzed using Lippert-Mataga polarity function, Reichardt's microscopic solvent polarity parameter, Kamlet's and Catalan's multiple linear regression approaches. Both general solute - solvent interactions and hydrogen bonding interactions are operative in these systems. However, the contribution of hydrogen bonding interactions is less compared to general solute-solvent interactions. The solvatochromic correlations are used to estimate excited state dipole moment using experimentally determined ground state dipole moment. The bathochromic shift of the emission spectra and the increase in excited state dipole moment indicate the intramolecular charge transfer (ICT) character in the emitting singlet state. The solvation studies in 1,4-dioxane - acetonitrile solvent mixture suggest that these dyes are preferentially solvated by 1,4-dioxane.

Crystal structure of 2-(5-meth-oxy-1-benzo-furan-3-yl)acetic acid.

The benzo-furan residue in the title compound, C11H10O4, is essentially planar (the r.m.s. deviation for the nine non-H atoms = 0.011 Å). While the meth-oxy group is coplanar with the fused ring system [C-C-O-C torsion angle = 3.1 (3)°], the acetic acid residue occupies a position almost prime [C-C-C-C = 77.0 (2)°]. In the crystal, centrosymmetrically related mol-ecules are linked by O-H⋯O hydrogen bonds to form eight-membered {⋯HOCO}2 synthons. The dimeric aggregates assemble into supra-molecular layers in the ab plane via benzene-C-H⋯O(ring) inter-actions.

Synthesis, structure-activity relationship of iodinated-4-aryloxymethyl-coumarins as potential anti-cancer and anti-mycobacterial agents.

A series of new iodinated-4-aryloxymethylcoumarins 6, 8 and 10 have been obtained from the reaction of various 4-bromomethylcoumarins 4 with 2-iodophenol 5, 3-iodophenol 7 and 4-iodophenol 9 respectively. All the title compounds were screened for anticancer activity against two cancer cell lines (MDA-MB human adenocarcinoma mammary gland and A-549 human lung carcinoma) and two mycobacterial strains (Mycobacterium tuberculosis H37 RV and Mycobacterium phlei). The SAR results indicate that nine compounds are potent, among these 10h and 10i having chlorine are most effective. This is the first report assigning in vitro anti-mycobacterial, anticancer and structure-activity relationship for this new class of iodinated-4-aryloxymethyl-coumarins.

6-Chloro-4-(4-methyl-phen-oxy-meth-yl)-2H-chromen-2-one.

In the title compound, C(17)H(13)ClO(3), the coumarin and phen-oxy moieties are essentially co-planar, making a dihedral angle of 1.99 (7)°. The phen-oxy moiety is oriented anti-periplanar with respect to the coumarin ring as indicated by the C-C-O-C angle of -179.97 (16)°. In the crystal, the sheet-like packing is stabilized by inter-molecular C-H⋯O and C-H⋯Cl hydrogen bonds.

Synthesis and antimicrobial studies on novel sulfonamides containing 4-azidomethyl coumarin.

A series of new and novel coumarin-6-sulfonamides with a free C4-azidomethyl group have been synthesized as antimicrobials in three steps starting from 7-methyl-4-bromomethylcoumarin 1. The reaction of 1 with chlorosulfonic acid was found to yield the corresponding 6-sulfonylchloride 2, which when treated with sodium azide led to intermediate 3. The title sulfonamides 5a-y were obtained from the reaction of 3 with various aromatic amines 4 in refluxing benzene. The chemical structures of the compounds were elucidated by IR, NMR and LC-MS spectral data. All the synthesized compounds have been screened for their in vitro anti-bacterial and anti-fungal activities. Some of the compounds have been found to be active against both bacterial species at a concentration of 1 microg/mL.

4-Azido-methyl-7-methyl-2-oxo-2H-chromene-6-sulfonyl azide.

In the title compound, C(11)H(8)N(6)O(4)S, the plane of the coumarin aromatic ring is twisted by 17.2 (2)° with respect to the plane of the azide group bound to the methyl-ene substituent, whereas it is twisted by 83.2 (2)° to the plane of the azide attached to the sulfonyl group. The crystal structure is stabilized by weak C-H⋯O inter-actions, leading to the formation of dimers with R(2) (2)(12) graph-set motifs. These dimers are further linked by weak S-O⋯π and π-π contacts [centroid-centroid distance = 3.765 (2) Å], leading to the formation of a layered structure.

4-Bromo-methyl-6-meth-oxy-2H-chromen-2-one.

The structure of the title coumarin derivative, C(11)H(9)BrO(3), is stabilized by weak inter-molecular C-H⋯O hydrogen bonds.

4-Bromo-methyl-7,8-dimethyl-coumarin.

In the title mol-ecule, C(12)H(11)BrO(2), all non-H atoms with the exception of the Br atom are essentially coplanar (r.m.s. deviation = 0.018 Å). The C-Br bond is inclined by 80.17 (12)° to this plane. The crystal structure is stabilized by weak C-H⋯O hydrogen bonds.